Semi-trailer trucks are frequently used to pull semi-trailers to haul cargo over roads. It is often desirable to know the weight of the cargo that the semi-trailer is hauling. FIG. 1A, for example, is a schematic side view of a first conventional system 10a for measuring the weight of cargo carried by a semi-trailer 12. As shown in FIG. 1A, the first system 10a includes a semi-trailer truck 20 that is coupled to the semi-trailer 12 via a fifth wheel coupling 22. The semi-trailer 12 includes rear suspension 14 (e.g., wheels, shocks, etc.), and the fifth wheel coupling 22 that attaches to the semi-trailer truck 20, generally over the truck's rear suspension 24 (e.g., wheels, shocks, etc.). The first system 10a also includes a rear load sensing assembly 16 positioned on or in the semi-trailer's 12 rear suspension 14, and a front load cell 18 positioned between the semi-trailer 12 and the truck's rear suspension 24. The rear load sensing assembly 16 and the front load cell 18 are designed to detect the weight of the load in the semi-trailer 12 while the semi-trailer 12 is coupled to the truck 20. The rear load sensing assembly 16 and the front load cell 18 can also be coupled to a display 26. The display 26 can be positioned in the truck 20 or at other locations to provide convenient access for a user.
In some instances, it is also desirable to determine the weight of the cargo in the semi-trailer 12 when the semi-trailer 12 is not coupled to the truck 20. FIG. 1B, for example, is a schematic side view of a second conventional system 10b for measuring the weight of the cargo of a semi-trailer 12 that is parked and detached from a corresponding semi-trailer truck. As shown in FIG. 1B, the rear suspension 14 supports the rear portion of the semi-trailer 12 with the corresponding rear load sensing assembly 16 between the rear suspension 14 and the semi-trailer 12. The front portion of the semi-trailer 12, however, is supported by landing gear or struts 28 extending from the front of the semi-trailer 12. The landing gear 28 can extend or pivot relative to the semi-trailer 12 between the extended position shown in FIG. 1B, and a stowed position adjacent to the semi-trailer 12 when the semi-trailer 12 is coupled to a truck. The second system 10b also includes a front load cell 18 positioned beneath the landing gear 28 (i.e., between the landing gear 28 and the ground). In this manner, the rear load sensing assembly 16 and the front load cell 18 are designed to detect the weight of the load in the semi-trailer 12 when the semi-trailer 12 is free standing. The rear load sensing assembly 16 and the front load cell 18 can also be coupled to a display 26.